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  • 1
    ISSN: 1745-4581
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A membrane separator/bioreactor system was developed for rapid detection of Escherichia coli O157:H7. The system consisted of a membrane separator/bioreactor (0.45 μm of the pore size) to separate the-complexes of E. coli O157:H7 and alkaline phosphatase-conjugated anti-E. coli O157:H7 antibodies from the sample and to produce p-nitrophenol through the enzymatic reaction (p-nitrophenyl phosphate hydrolysis), and an optical detector for measuring the p-nitrophenol absorbance at 400 nm. The membrane material and the flow rate of the substrate for the enzymatic hydrolysis had great effects on the absorbance of p-nitrophenol. The optimum conditions for the enzymatic reaction were determined as 1.0 M Tris buffer, pH 8.0, and 0.1 M MgCl2 for this system. The detection range was 104± 107 CFU/mL with a relative standard deviation of 4.3 ± 14.2%, and whole procedure could be completed in 50 min without any enrichment and culture. Other bacteria such as Salmonella typhimurium, Campylobacter jejuni and Listeria monocytogenes had no significant interference with the detection of E. coli O157:H7.
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  • 2
    ISSN: 1745-4565
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Electrical stimulation was evaluated as a method to kill Salmonella typhimurium in various salt solutions at different concentration. Salmonella typhimurium at 2 × 105 CFU/ml was treated at 22–24C for 60 min in each salt solution using electricity at 10 mA/cm2 current, 1 kHz frequency, and 50% duty cycle. Samples taken at various times were serially diluted, plated on tryptic soy agar and xylose lysine desoxycholate agar, and incubated at 37C for 18–24 h. To detect injured cells, samples were also pre-enriched in buffered peptone water at 37C for 4–5h before being plated. Results indicated all salmonellae were electrically killed at 5 min in NaCl, at 30 min in NaNO3, and at 45 min in NaC2H3O2 at 0.15 and 0.015 M concentrations. Salmonellae were also killed at 45 min in Na3PO4 and at 60 min in Na2CO3 at 0.0015 M concentration by electricity in combination with high pH.
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  • 3
    ISSN: 1745-4581
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A bienzyme (tyrosinase and horseradish peroxidase) electrochemical biosensor was developed for detection of Salmonella typhimurium, and evaluated for application in a flow injection system coupled with immunomagnetic separation for food samples. Parameters for immunomagnetic separation, enzymatic reaction, flow injection and electrochemical detection were determined using pure culture samples. The selectivity was tested in the presence of Listeria monocytogenes, Campylobacter jejuni and E. coli 0157:H7. The results showed a linear relationship for logarithmic values between peak current ratio and the cell number of S. typhimurium in the range of 103 105 cfu/mL, with R2= 0.99. The detection limit of this method was 1.09 × 103 cfu/mL for S. typhimurium and the detection time was 2.5 h. Samples of chicken carcass wash water and ground beef were used to evaluate the biosensor. The results demonstrated that this biosensor has a potential for rapid detection of different pathogens in various food samples.
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  • 4
    ISSN: 1745-4581
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A DNA binding fluorescence method based on polymerase chain reaction (PCR) products was evaluated for rapid detection of Salmonella Typhimurium in poultry products. Wash water samples of chicken carcasses and ground turkey were inoculated with S. Typhimurium to obtain final concentrations of 10° - 105 CFU/mL. One mL of each sample was used to get the DNA template and 5 μL of the sample template was added into 25 μL of SYBR Green PCR Master Mix and two specific Salmonella ompC gene primers. The negative control was the same except 5 μL of each wash solution was added instead of 5 μL sample template. The reaction was carried out in a thermocycler. Finally, the fluorescence signal of each PCR product was measured using a fluorometer. The PCR products were also confirmed by ethidium bromide agarose gel, and the DNA concentrations of the PCR products were measured by a filter fluorescence photometer. The results showed that when bacterial cells increased from 0 to 2 CFU/mL, the fluorescence signal increased significantly. The PCR-based fluorescence method could detect the target bacteria in minutes after PCR amplification compared to hours by gel electrophoresis and also could be done at an earlier time during PCR amplification. The detection limit of this method for S. Typhimurium in the poultry samples was 2 CFU/mL without any enrichment.
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  • 5
    ISSN: 1745-4581
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A chemiluminescence biosensor, using a fiber-optic-linked photometer and a data acquisition unit connected to a PC, was developed in conjunction with immunomagnetic separation for rapid detection of Salmonella Typhimurium. Magnetic microbeads coated with Anti-Salmonella antibodies and anti-Salmonella antibodies conjugated with horseradish peroxidase (HRP) were added to artificially-inoculated samples, and the immuno-reaction was completed in 60 min resulting in a sandwich complex. A magnetic field was applied to collect magnetic beads and the addition of luminol to HRP-conjugated antibodies resulted in a chemiluminescence reaction. The signal was collected through a fiber optic light guide, measured with a photometer, and recorded in the data acquisition unit. The minimum detection limit of the chemiluminescence biosensor for S. Typhimurium was 1.97 × 103 CFU/mL and the range of the detectable signal was from 8.6 to 350 mV for cell numbers from 1.97 × 103 to 1.97 × 106 CFU/mL. Signal values for 106 CFU/mL of S. Typhimurium were at least 97 and 394% higher than the corresponding values for S. enteritidis and four times the signal values for others including S. montevideo, S. california, S. heidlberg, and S. seftenberg, respectively. The biosensor response showed a significant difference (P 〈 0.05) between 103 CFU/mL S. Typhimurium and 106 CFU/mL of commonly-occurring bacteria in foods including Listeria monocytogenes, Pseudomonas aeruginosa, Citrobacter freundii, Campylobacter jejuni, Escherichia coli O157, and generic Escherichia coli. A regression equation, V = 0.0262 N 5.7713, with R2= 0.9713 was obtained for the calibration curve over the detection range for S. Typhimurium. The whole procedure could be completed within 90 min.
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  • 6
    ISSN: 1745-4581
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract  Growth of Listeria monocytogenes in a Listeria enrichment broth (LEB) was automatically monitored by electrochemical cyclic voltammetric scan using a gold working electrode. Changes in cyclic voltammograms were observed during growth of L. monocytogenes in LEB. The reduction peak at −0.4 V (vs Ag/AgCl) corresponding to the reduction of oxygen dissolved in LEB on cyclic voltammograms was decreasing with proliferation of L. monocytogenes, and disappeared eventually. A pair of reversible redox peaks appeared during growth of L. monocytogenes in LEB. These cyclic voltammetric characteristics can be used to detect L. monocytogenes in various samples. Threshold values (detection time) obtained from the oxygen consumption curves were inversely related to the concentrations of L. monocytogenes in the broth. A calibration curve was obtained by plotting initial cell concentrations (CFU/mL) determined by conventional plate counting, as a function of the detection time. A linear response was found on the calibration curve for L. monocytogenes between 1 ∼ 9 times 100 and 1 ∼ 9 times 105 cells/mL. The detection time was approximately 17 and 6 h for 1 ∼ 9 times 100 and 1 ∼ 9 × 105 cells/mL of viable L. monocytogenes in the broth, respectively. The method was evaluated in detection of L. monocytogenes in milk samples.
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  • 7
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Chicken skins inoculated with Salmonella typhimurium at 1 × 108 CFU/mL were subjected to chemical or electrical treatments (4 mA/ cm2 current, 1 kHz frequency and 50% duty cycle) for 10 min in 1% sodium chloride (NaCl), sodium carbonate (Na2CO3), or trisodium phosphate (Na3PO4 12H2O or TSP). Salmonellae on chicken skins and in treatment solutions and rinsing water were enumerated with microbiological platings. Chicken skin was also examined using scanning electron microscopy.S. typhimurium attached to skins were reduced by 90% after electrical treatments in 1% NaCl, Na2CO3, or TSP, while the reduction ranged from 34% to 76% in groups treated by the salts alone.
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  • 8
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A test chamber was designed and constructed and prechill chicken carcasses inoculated with Salmonella typhimurium were treated in it. They were sprayed with tap water, 0.85% sodium chloride (NaCl), 5% or 10% trisodium phosphate (TSP), 5% or 10% sodium bisulfate (SBS), 0.1% cetylpyridinium chloride (CPC), or 1% lactic acids (LAC) at 207, 345 or 827 kPa pressure for either 30 or 90 sec exposure time. Samples were taken from carcass wash water to determine the most probable number of Salmonella. Compared to tap water spraying, 0.85% NaCl spraying did not significantly reduce Salmonella. The greatest reductions of S. typhimurium, by 10% TSP, 10% SBS, 0.1% CPC or 1% LAC spraying, were 3.7, 2.4, 1.6 or 1.6 log in 90 sec treatments, respectively.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 63 (1998), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Chemical spray parameters, including temperature, pressure and exposure time, were evaluated for their effects on reducing Salmonella typhimurium on chicken skins. Pre-chilled chicken carcass skins were inoculated with S. typhimurium and sprayed with 0.1% cetylpyridinium chloride (CPC), 10% trisodium phosphate (TSP), or 2% lactic acid (LA). In the CPC spray, the 40°C treatments resulted in the greatest bacterial reduction. The most effective spray temperatures for LA and TSP treatments were 40 to 55°C. All chemical spray treatments at 207–1034 kPa reduced S. typhimurium. The reduction of S. typhimurium was greatest in all treatments when sprayed with 90 sec spray and 90 sec setting time.
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